The present invention relates to a combined pronation and supination control plantar insert for shoes.
From a functional point of view, the foot behaves like a propeller whose blades are constituted by the hindfoot and the forefoot.
The rolling action of a step can be seen as consisting of three phases: a first contact phase, a second resting phase and a third propulsion phase.
During the first contact phase, the foot tends to pronate and therefore arrange itself inward; during the second resting phase, the foot stiffens and tends to supinate, so that the weight tends to shift toward the outer part of the foot; during the third propulsion phase, the foot is in a central position with a slight pronation in order to give impetus to the step.
All these movements of the foot can be considered equivalent to the motion of a propeller.
Therefore, depending on the motion of the blades, the foot relaxes and flattens or stiffens and therefore becomes hollow.
These two relaxation and stiffening phases are the two movements that occur alternatively in the foot during upright posture, running and jumping, and are known as pronation and supination respectively.
The deformities commonly known as flatfoot and hollow foot are due to predominant or persistent pronation (flatfoot) or supination (hollow foot).
Ready-made plantar inserts are commercially available in order to control the movement of the foot but they are usually scarcely useful.
Their use is often discretionary and can cause damage if said plantar inserts are incautiously worn by careless users.
Customizable plantar inserts manufactured by specialized technicians are an altogether different matter.
In this case, the final product is customized and perfectly matches the foot of the patient.
However, this requires the aid of labor-intensive techniques (plaster cast of the foot and creation of a complementary shape, assembly of different materials, refinement of the complementary shape according to the defect to be corrected, etcetera) and accordingly entails long production times.
Costs are high and it is impossible to modify the configuration of said plantar inserts if changes in the foot and/or in the structure of the bones, joints and muscles occur.
All these are only some of the main problems of this kind of plantar inserts.
It should also be noted that the bad posture of the feet does not affect only the bone, joint and muscle structures of said foot, causing various localized disorders; it also affects the entire supra- and subsegmental posture; accordingly, alterations can occur which affect not only the foot and the joints closest to it (talocrural joint, coxofemoral joint, knee joint) but also more distal articulations (interchondral joints, costovertebral joints, etcetera).
Many of the alterations affecting the cervical column and related symptoms, reaching as far as the temporomandibular joint with consequences for mastication, can in all likelihood originate from the incorrect static and dynamic posture of the foot.